Many cardiac arrhythmia's that formerly required the use of potentially toxic drugs or cardiac surgery can now be routinely cured (or at least palliated) in the electrophysiology laboratory by means of transcatheter ablation techniques. As shown in conjunction with FIG. 1, the basic idea behind transcatheter ablation is to position an electrode catheter to a critical area within the heart 52, and to apply damaging energy through the catheter in order to create a discrete scar. Strategically placed scar tissue, since it is electrically inert, can disrupt the pathways necessary for pathologic tachyarrhythmias.
A novel PC based system disclosed here, interfaces with both the patient and the ablation generator for providing added safety to the ablation procedure. Such a system finds uses in different types of cardiac ablation procedures, particularly left atrial ablations for atrial fibrillation, and slow pathway modification for providing ablation therapy of AV nodel reentry tachycardia.
A V nodal reentrant tachycardia (AVNRT) is the most common type of reentrant supraventricular tachycardia, and is the operative mechanism in up to 60% of patients presenting with paroxysmal atrial tachycardia (PAT). In AV nodal reentry, the reentrant circuit is usually said to be enclosed within the AV node. In patients with AV nodal reentry, the AV node is functionally divided into two longitudinal pathways (dual AV nodal pathways). These dual pathways form the reentrant circuit. Because the reentrant circuit in AV nodal reentry, for all practical purposes, involves the AV node exclusively, this arrhythmia responds well to autonomic maneuvers and drugs that affect the AV node (digitalis, calcium blockers, and β blockers). Ablation for AV nodal reentry tachycardia is typically performed using radiofrequency (RF) catheter ablation, or cryoablation.
During the past decade, RF ablation and cryoablation has become the treatment of choice for AV nodal reentrant tachycardia. Successfully ablating AV nodal reentrant tachycardia has required a change in the way electrophysiologists visualize the AV node. In the past, most electrophysiologists thought of the AV node simply as a compact, button-like structure. The AV node does indeed appear to have a compact distal component (i.e, the part of the node that gives rise to the His bundle), but the more proximal portion of the AV node appears to be “diffuse”.
The tracts of atrial fibers that coalesce to form the AV node are ill defined. It now appears that (at least in patients with AV nodal reentrant tachycardia and probably in all individuals), two distinct tracts can be localized anatomically—the anterior tract (which corresponds to the fast AV nodal pathway), and the posterior tract (which corresponds to the slow AV nodal pathway).
In patients with AV nodal reentrant tachycardis, the fast and slow pathways can be visualized as two tracts of atrial fibers that coalesce to form the compact AV node. The fast pathway is an anterior and superior tract of fibers, located along the tendon of Todaro. The slow pathway is a posterior and inferior tract of fibers, located along the tricuspid annulus near the os of the coronary sinus. Thus, the anatomic correlate of the “functional” dual AV nodal pathways have now been identified. Because the two pathways can be discretely localized, they can be discretely ablated. Even though the fast pathway can also be ablated, the ablation of AV nodal reentry is now generally accomplished by ablating the slow pathway, since the slow pathway is posterior, and relatively distinct from the AV node.
Even though the success rate of AVNRT ablation is very high, many patients end up with heart block. The heart block may be temporary or permanent. Patients with temporary heart block recover, however if patients AV conduction does not recover spontaneously, a cardiac pacemaker and lead(s) are implanted. These patients become pacemaker dependent for the rest of their lives. Considering that some of these patients are relatively young, there is a real need for a method and system that would increase the safety of cardiac ablation procedures, especially for common ablation procedures, such as ablations for AVNRT and atrial fibrillation.
This patent application is directed to novel method and system for monitoring the ablation procedure, and under certain conditions either shutting off power to the ablation generator or disconnecting the ablation circuit, whereby preventing excessive energy to get to the cardiac tissues, and reducing and/or eliminating the chances of developing complete heart block in AV nodal reentry tachycardia ablation procedures.